Castings are produced generally by forming molding sand into a casting mold having a cavity in it, with a wooden pattern or a die, and, having arranged a core if necessary in the cavity, casting molten metal to the cavity.
Production of wooden pattern and dies requires skills in manufacturing and needs expensive facilities, and there arises the problem of disposal together with disadvantages such as high price and heavy weight, and their use is difficult except for mass-produced castings. The shape of a sand mold using molding sand is retained by adding a binder to usual sand and hardening it, and thus a regeneration process is essential for reutilizing the sand. In the regeneration process, there arises a problem such as generation of waste material such as dust. When a core is produced with sand casting, there is not only the problem described above but also difficulty in handling because of the weight of the core itself, and contradictory performance, that is, strength retention during casting and removability of the core after casting, is required.
For techniques of solving such problems, it is known that members used in casting molds are formed from, for example, organic-fiber products such as paper (see JP-A (U)6-86843), from inorganic fibers as a major component to which resin is added as a binder (see JP-A 10-5931), or from cellulose fibers to which inorganic powder or inorganic fibers are added (see JP-A 9-253792). A composition for forming a molding core comprising a refractory inorganic granular matter, inorganic and organic fibrous substances and a binder matter is also known (see JP-A 2003-230940).